Stratigraphic pollen analysis performed on a late Pleistocene cypress forest preserved on the northern Gulf of Mexico continental shelf

Abstract

ABSTRACTStratigraphic pollen analysis of terrestrial peat–mud layers from a buried bald cypress (Taxodium distichum) forest allows study of autochthonous fossil pollen profiles from a glacial refugium along the northern Gulf of Mexico coast in the context of fluctuating sea levels. The site is in 18 m of water, offshore from Orange Beach, Alabama, USA. Exposed cypress stumps are in growth position, still rooted in sediment. Radiocarbon dating of peat and optically stimulated luminescence dating of subjacent sediments yielded an age range of 72–45 ka. We hypothesize the site was rapidly buried by floodplain aggradation from pulsed sea‐level rise during the glacial interval. Pollen results from the lowermost peat layer are consistent with a bald cypress − tupelo gum (Nyssa aquatica) backwater forest. This was followed by a brief transitional period where the pollen assemblage is similar to Atlantic Coastal Plain Blackwater Levee/Bar Forests, but may be evidence of a no‐modern analog community. Final Pleistocene pollen spectra indicate a more open environment, dominated by grasses (Poaceae) and sedges (Cyperaceae).